Recombinant retroviruses can be used for gene transfer and are under consideration for use in gene therapy (Science 260:926-932, 1993), e.g., for in vivo or ex vivo gene therapy either as vectors targeted to specific tissues or as lenti-virus vectors that transduce non-dividing cells. The relatively large size (e.g., ˜100 nm) and complexity of the retroviruses, as well as their instability and sensitivity to inhibitors have presented significant challenges to the development of processes for the purification and concentration of viruses, particularly when large-scale production is desired. However, several problems limit the effectiveness of recombinant retroviruses, including relatively low titers of viruses, instability of the particles, and the lack of facile methods for the rapid concentration and purification of bioactive viral particles (Hum. Gene Ther., 5:19-28, 1994; Bioseparation, 6:211-288, 1996; Curr. Opin. Biotechnol., 9:177-185, 1998; Biotechnol. Prog., 15:1-11, 1999). The development of new processes for the production of stable, concentrated recombinant retroviruses that can yield high gene transfer efficiencies is thus one of several challenges facing the field of gene therapy. Moreover, as applications of in vivo gene transfer become more numerous, methods for the large-scale purification of viruses will also be required.
Additionally, a need exists for inexpensive, rapid, and effective methods for removing viruses from pooled plasma (e.g., as identified, for example, by the Consortium for Plasma Science LLC), plasma derivatives, blood banks, living tissue, a patient's blood, or commercial biological products (e.g., complex biopharmaceutical preparations such as recombinant protein preparations).